Multisleeve stabilizer

ABSTRACT

A stabilizer for stabilizing or centering a drill string in a drill bore such as employed for oil and gas wells is provided. The stabilizer comprises a plurality of sleeves having a cylindrical inside surface surrounding a mandrel and having a cylindrical outside surface for engaging a well bore. Longitudinally extending recessed portions in the outer cylindrical surface permit circulation of drilling fluids. Preferably the outer cylindrical surface is provided with a wearresistant, hard-facing alloy. A female fitting is provided at one end of each sleeve and a complementary male fitting at the opposite end so that a plurality of sleeves can be interconnected and connected to a male fitting on the mandrel. A female sleeve protects the unused male fitting and includes a notch for engagement with a lock stud on the mandrel.

United States Patent Van Note 1 Feb. 15, 1972 s2| u.s.c|. .175/325, 308/4A 51| lnt.Cl .1121 17/10 ss| FieldolSearch ..l75/325,76; 166/241;308/4A [56] References Cited UNITED STATES PATENTS 1,701,427 2/1929 Shields 2,021,451 11/1935 Johnson 308/4 A 1,844,371 2/1932 Santigo 308/4 A 1,912,854 6/1933 Osgood... 175/325 2,034,075 3/1936 Wright..... 308/4 A 2,079,449 5/1937 Haldeman 175/325 Primary Examiner-James A. Leppink Al!orneyChristie, Parker & Hale [57] ABSTRACT A stabilizer for stabilizing or centering a drill string in a drill bore such as employed for oil and gas wells is provided. The stabilizer comprises a plurality of sleeves having a cylindrical inside surface surrounding a mandrel and having a cylindrical outside surface for engaging a well bore. longitudinally extending recessed portions in the outer cylindrical surface permit circulation of drilling fluids. Preferably the outer cylindrical surface is provided with a wear-resistant, hard-facing alloy. A female fitting is provided at one end of each sleeve and a complementary male fitting at the opposite end so that a plurality of sleeves can be interconnected and connected to a male fitting on the mandrel. A female sleeve protects the unused male fitting and includes a notch for engagement with a lock stud on the mandrel.

4 Claims, 2 Drawing Figures MULTISLEEVE STABILIZER BACKGROUND Stabilizers are employed in deep hole drilling, such as employed for oil and gas wells, for centering the drill string in the well bore and localizing wear of the drill string on the stabilizer rather than the string itself. In particular, a stabilizer is highly desirable adjacent the drill bit for preventing the bit from following formation dip tendency and reducing hole wandering, doglegs, wall sticking and the like.

Prior stabilizers have been in two forms. One comprises a separate element inserted in the drill string and jointed to the string in a conventional manner. These stabilizers are essentially cylindricalbodies threaded at each end for insertion in the drill string and having a plurality of ribs or the like for engaging the well bore. The other type of stabilizer comprises a mandrel having a centering sleeve fitted on the mandrel so that the sleeve can be replaced when worn with less expense than a one-piece stabilizer.

The stabilizers are items used up" in the drilling of a well since the portion of the stabilizer that engages the well bore is subjected to extreme wear conditions and eventually becomes of sufficiently reduced diameter to be substantially ineffective in stabilizing the drill string. When this occurs, the stabilizer is removed and replaced with a new or refurbished one. The worn stabilizers are either discarded or returned to a shop for reconstruction.

Since a large number of stabilizers may be employed in drilling a deep hole, it-is necessary to have an inventory of stabilizers on hand at the drill rig. In some formations it is desirable to use a long stabilizer and in others a short unit is preferred for minimized expense. Previously it has not been possible to provide the driller in the field with operational flexibility in the stabilizers available to him since a change in stabilizer requires additional inventory in the field. It may become desirable in some circumstances during drilling operations to employ a different type or length of stabilizer than originally employed in the hole, and in the absence of a substantial inventory of stabilizers at the drill rig this has previously been impractical.

BRIEF SUMMARY OF THE INVENTION Therefore, in practice of this invention according to a preferred embodiment there is provided a stabilizer sleeve for deep hole drilling comprising an inner cylindrical surface for fitting on an elongated cylindrical mandrel, a cylindrical outside surface for stabilization of a drill string in a borehole, a plurality of recessed portions from the outside surface for circulating drilling fluid, and first and second mating connector parts at opposite endsof the sleeve with the first and second connector parts being mutually complementary for serially interconnecting a plurality of similar sleeves. A plurality of such sleeves are assembled on a mandrel for improved stabilization. Spacer sleeves may be employed for positioning or separating the stabilizer sleeves.

DRAWINGS These and other features and advantages of the invention will be appreciated as same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings:

FIG. 1 illustrates in longitudinal cross section a stabilizer constructed according to principles of this invention;

FIG. 2 is a transverse cross section of the stabilizer of FIG. 1.

DESCRIPTION FIG. 1 illustrates in longitudinal cross section a multisleeve stabilizer constructed according to principles of this invention and providing considerable flexibility in field use of the stabilizer. As illustrated in this embodiment there is provided a mandrel 10, the upper end of which is not shown but is connectable by a conventional threaded joint to a drill string. In a typical embodiment, the mandrel 10 is in the order of 6 to 8 inches in diameter and includes an axial hole 1 l for down-hole circulation of drilling fluids. The lower end of the mandrel includes a female threaded fitting l2 complementary to the male fitting at the upper end of the mandrel so that the mandrel can be fitted into any selectedposition along the length of a drill string. Typically, at least one mandrel is connected in the drill string immediately adjacent the bit for stabilizing the lower end of the drill string. The mandrel includes sufficient length for conventional drill rig tongs for' breaking and making up the drill string.

Toward the upper end of the mandrel I0 is an enlarged cylindrical portion 13 immediately below which is a conventional male thread 14. The enlarged cylindrical portion 13 provides mechanical protection for the male threads 14 and also provides additional material for cutting new threads if the threaded portion 14 is damaged.

Threaded onto the male threads 14 by female threads I6 complementary thereto, is a sleeve stabilizer 17. The sleeve has a cylindrical inside surface 18 fitting on the outside surface of the mandrel 10. In the central portionof the sleeve there is an outer cylindrical surface 19 having a diameter appropriate for engaging the inside of a well bore with any desired clearance. The outside surface 19 is preferably formed of a conventional hard-facing alloy'having appreciable wear resistance since this surface engages the well bore and is subjected to extreme wear conditions, and the hard facing assures a long lifetime. The outer cylindrical surface 19 is interrupted by a plurality of longitudinally extending recessed portions 21, which permit up-hole circulation of drilling fluids. In the illustrated embodiment there are four broad radially extending blades forming the external cylindrical surface 19 and four intermediate recessed portions 21 for permitting up-hole circulation. The four blades may extend longitudinally along the length of the sleeve parallel to the sleeve axis or may be arranged in a helical path around the sleeve, as desired. If preferred, three blades, six blades or other cross-sectional configurations may be employed for providing an interrupted cylindrical external surface for stabilizing in the well bore and having recessed portions for up-hole circulation of drilling fluids.

A skirt 20 at the female threaded end of the sleeve 17 provides for engagement of the sleeve by conventional drill rig tongs, eliminating any necessity for special breakers for removing sleeves from the assembly.

The lower end of the sleeve 17 has a male thread 22 exactly complementary to the female thread 16 at the opposite end of the sleeve. Threaded onto the male thread 22 by a complementary female thread 23 is a second stabilizer sleeve 24. In the illustrated embodiment the second sleeve 24 is substantially identical to the first sleeve 17 and has an outer cylindrical portion 26 for engagement with the well bore and an inner cylindrical surface 27 for engaging the cylindrical mandrel 10. A different arrangement for the well bore engaging surface 26 as compared with the similar engaging surface 19 on the first sleeve can be employed if desired. Thus, for example, a threebladed stabilizer sleeve can be used in combination with a four-bladed stabilizer sleeve so long as the male and female threads at the ends of the sleeve are complementary. Similarly, a spacer sleeve having no blades can be employed for spacing one or more stabilizer sleeves at selected locations along a mandrel.

The second sleeve 24 has a male threaded portion 28 at its lower end which is engaged by a complementary female threaded portion 29 on a protecting sleeve 31. The protective sleeve 31 serves to protect the male threads 28 from mechanical damage during use of the stabilizer. In addition, the protective sleeve 31 includes a notch 32 at its lower end. A stud 33, such as, for example, a capscrew is threaded into the mandrel 10. The stud 33 serves to prevent the several sleeves from falling down the hole in case the various threaded joints become disengaged. The notch 32 may engage the stud 33 to prevent spinning of the sleeves during washover. If desired, the notch 32 can be in a J-shape for engagement with the stud in a direction of thread loosening and disengagement in a direction of thread tightening.

Although the one embodiment of this invention has been described and illustrated herein, many modifications and variations will be apparent to one skilled in the art. Thus, for example, the threads for joining the sleeves to each other and to the mandrel can be replaced with other fastening means so long as the fasteners at opposite ends of the sleeves are complementary. Likewise, the effective length of the stabilizer and the number, style, and size of sleeves fitted thereon can be varied according to the requirements of the drilling operation without stocking a large inventory of special stabilizers in the field. By incorporating a plurality of sleeves on a single mandrel, the number of working joints along the drill string is maintained constant despite the enhanced stabilization of a plurality of stabilizers. Many other modifications and variations will be apparent to one skilled in the art and it is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A combination comprising:

a substantially cylindrical mandrel including mating portions at the upper and lower ends respectively for connection of the mandrel into a borehole drill string, and a male threaded portion intermediate the ends;

a first stabilizer sleeve on the mandrel and including an outer cylindrical surface for engaging a borehole, a plurality of recessed portions in the outer cylindrical surface for permitting drilling fluid circulation, a female threaded portion at one end of the sleeve and a male threaded portion complementary to the female threaded portion at the other end of the sleeve, the female threaded portion being engaged with the male threaded portion on the mandrel;

a second sleeve on the mandrel and including a female threaded portion complementary to and engaged with the male threaded portion on the first sleeve and a male threaded portion complementary with the female threaded portion on the opposite end of the second sleeve.

2. A combination as defined in claim 1 further comprising:

a protecting sleeve having a female threaded portion engaged with the male threaded portion on the second sleeve; and

a locking stud on the mandrel adjacent the protecting sleeve.

3. A combination as defined in claim 2 wherein the second sleeve comprises a stabilizer sleeve having an outer cylindrical surface for engaging a borehole, and a plurality of recessed portions in the outer cylindrical surface for permitting drilling fluid circulation.

4. A combination as defined in claim 1 further comprising a spacer sleeve having an outside diameter smaller than the outer cylindrical surface and having complementary female threads engaged with the male threaded'portion of the mandrel, and complementary male threads engaged with the female threaded portion on the first stabilizer sleeve. 

1. A combination comprising: a substantially cylindrical mandrel including mating portions at the upper and lower ends respectively for connection of the mandrel into a borehole drill string, and a male threaded portion intermediate the ends; a first stabilizer sleeve on the mandrel and including an outer cylindrical surface for engaging a borehole, a plurality of recessed portions in the outer cylindrical surface for permitting drilling fluid circulation, a female threaded portion at one end of the sleeve and a male threaded portion complementary to the female threaded portion at the other end of the sleeve, the female threaded portion being engaged with the male threaded portion on the mandrel; a second sleeve on the mandrel and including a female threaded portion complementary to and engaged with the male threaded portion on the first sleeve and a male threaded portion complementary with the female threaded portion on the opposite end of the second sleeve.
 2. A combination as defined in claim 1 further comprising: a protecting sleeve having a female threaded portion engaged with the male threaded portion on the second sleeve; and a locking stud on the mandrel adjacent the protecting slEeve.
 3. A combination as defined in claim 2 wherein the second sleeve comprises a stabilizer sleeve having an outer cylindrical surface for engaging a borehole, and a plurality of recessed portions in the outer cylindrical surface for permitting drilling fluid circulation.
 4. A combination as defined in claim 1 further comprising a spacer sleeve having an outside diameter smaller than the outer cylindrical surface and having complementary female threads engaged with the male threaded portion of the mandrel, and complementary male threads engaged with the female threaded portion on the first stabilizer sleeve. 